Add user registration emails + email infrastructure (#150)

* Add email functionality

* Add email template project and rendering service

* Update email template dir structure

* Add email header and footer components for user registration template

* update example env

* Refactor email templates namespace and components

* Format email dir

.env.example

@@ -36,3 +36,19 @@ DB_PASSWORD=YourStrong!Passw0rd
 # IMPORTANT: Generate a secure secret (minimum 32 characters)
 # Command: openssl rand -base64 32
 JWT_SECRET=128490218jfklsdajfdsa90f8sd0fid0safasr31jl2k1j4AFSDR
+
+
+# ======================
+# SMTP Configuration
+# ======================
+# SMTP settings for sending emails (e.g., password resets)
+# For development, you can use a local SMTP testing tool like Mailpit or MailHog
+# In production, set these to real SMTP server credentials from an email service
+# provider (e.g., SendGrid, Mailgun, Amazon SES).
+SMTP_HOST=mailpit
+SMTP_PORT=1025
+SMTP_USERNAME=
+SMTP_PASSWORD=
+SMTP_USE_SSL=false
+SMTP_FROM_EMAIL=noreply@thebiergarten.app
+SMTP_FROM_NAME=The Biergarten App

docker-compose.dev.yaml

@@ -98,6 +98,19 @@ services:
     volumes:
       - nuget-cache-dev:/root/.nuget/packages
 
+  mailpit:
+      image: axllent/mailpit:latest
+      container_name: dev-env-mailpit
+      ports:
+        - "8025:8025"  # Web UI
+        - "1025:1025"  # SMTP server
+
+      restart: unless-stopped
+      environment:
+        MP_SMTP_AUTH_ACCEPT_ANY: 1
+        MP_SMTP_AUTH_ALLOW_INSECURE: 1
+      networks:
+        - devnet
 volumes:
   sqlserverdata-dev:
     driver: local

src/Core/API/API.Core/API.Core.csproj

@@ -20,7 +20,12 @@
   <ItemGroup>
     <ProjectReference Include="..\..\Domain.Entities\Domain.Entities.csproj" />
     <ProjectReference Include="..\..\Domain.Exceptions\Domain.Exceptions.csproj" />
-    <ProjectReference Include="..\..\Infrastructure\Infrastructure.Repository\Infrastructure.Repository.csproj" />
+    <ProjectReference
+      Include="..\..\Infrastructure\Infrastructure.Email\Infrastructure.Email.csproj" />
+    <ProjectReference
+      Include="..\..\Infrastructure\Infrastructure.Email.Templates\Infrastructure.Email.Templates.csproj" />
+    <ProjectReference
+      Include="..\..\Infrastructure\Infrastructure.Repository\Infrastructure.Repository.csproj" />
     <ProjectReference Include="..\..\Infrastructure\Infrastructure.Jwt\Infrastructure.Jwt.csproj" />
     <ProjectReference Include="..\..\Service\Service.Auth\Service.Auth.csproj" />
     <ProjectReference Include="..\..\Service\Service.UserManagement\Service.UserManagement.csproj" />

src/Core/API/API.Core/Dockerfile

@@ -14,6 +14,7 @@ COPY ["Domain.Exceptions/Domain.Exceptions.csproj", "Domain.Exceptions/"]
 COPY ["Infrastructure/Infrastructure.Repository/Infrastructure.Repository.csproj", "Infrastructure/Infrastructure.Repository/"]
 COPY ["Infrastructure/Infrastructure.Jwt/Infrastructure.Jwt.csproj", "Infrastructure/Infrastructure.Jwt/"]
 COPY ["Infrastructure/Infrastructure.PasswordHashing/Infrastructure.PasswordHashing.csproj", "Infrastructure/Infrastructure.PasswordHashing/"]
+COPY ["Infrastructure/Infrastructure.Email/Infrastructure.Email.csproj", "Infrastructure/Infrastructure.Email/"]
 COPY ["Service/Service.Auth/Service.Auth.csproj", "Service/Service.Auth/"]
 COPY ["Service/Service.UserManagement/Service.UserManagement.csproj", "Service/Service.UserManagement/"]
 RUN dotnet restore "API/API.Core/API.Core.csproj"

src/Core/API/API.Core/Program.cs

@@ -12,6 +12,9 @@ using Microsoft.AspNetCore.Mvc.Filters;
 using Service.Auth.Auth;
 using Service.UserManagement.User;
 using API.Core.Contracts.Common;
+using Infrastructure.Email;
+using Infrastructure.Email.Templates;
+using Infrastructure.Email.Templates.Rendering;
 
 var builder = WebApplication.CreateBuilder(args);
 
@@ -53,6 +56,8 @@ builder.Services.AddScoped<IRegisterService, RegisterService>();
 
 builder.Services.AddScoped<ITokenInfrastructure, JwtInfrastructure>();
 builder.Services.AddScoped<IPasswordInfrastructure, Argon2Infrastructure>();
+builder.Services.AddScoped<IEmailProvider, SmtpEmailProvider>();
+builder.Services.AddScoped<IEmailTemplateProvider, EmailTemplateProvider>();
 
 // Register the exception filter
 builder.Services.AddScoped<GlobalExceptionFilter>();

src/Core/API/API.Specs/API.Specs.csproj

@@ -17,7 +17,8 @@
     <!-- Reqnroll core, xUnit adapter and code-behind generator -->
     <PackageReference Include="Reqnroll" Version="3.3.3" />
     <PackageReference Include="Reqnroll.xUnit" Version="3.3.3" />
-    <PackageReference Include="Reqnroll.Tools.MsBuild.Generation" Version="3.3.3" PrivateAssets="all" />
+    <PackageReference Include="Reqnroll.Tools.MsBuild.Generation" Version="3.3.3"
+      PrivateAssets="all" />
 
     <!-- ASP.NET Core integration testing -->
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="9.0.1" />
@@ -34,5 +35,7 @@
 
   <ItemGroup>
     <ProjectReference Include="..\API.Core\API.Core.csproj" />
+    <ProjectReference
+      Include="..\..\Infrastructure\Infrastructure.Email\Infrastructure.Email.csproj" />
   </ItemGroup>
 </Project>

src/Core/API/API.Specs/Dockerfile

@@ -8,6 +8,7 @@ COPY ["Domain.Exceptions/Domain.Exceptions.csproj", "Domain.Exceptions/"]
 COPY ["Infrastructure/Infrastructure.Repository/Infrastructure.Repository.csproj", "Infrastructure/Infrastructure.Repository/"]
 COPY ["Infrastructure/Infrastructure.Jwt/Infrastructure.Jwt.csproj", "Infrastructure/Infrastructure.Jwt/"]
 COPY ["Infrastructure/Infrastructure.PasswordHashing/Infrastructure.PasswordHashing.csproj", "Infrastructure/Infrastructure.PasswordHashing/"]
+COPY ["Infrastructure/Infrastructure.Email/Infrastructure.Email.csproj", "Infrastructure/Infrastructure.Email/"]
 COPY ["Service/Service.Auth/Service.Auth.csproj", "Service/Service.Auth/"]
 COPY ["Service/Service.UserManagement/Service.UserManagement.csproj", "Service/Service.UserManagement/"]
 RUN dotnet restore "API/API.Specs/API.Specs.csproj"

src/Core/API/API.Specs/Mocks/MockEmailService.cs

@@ -0,0 +1,54 @@
+using Infrastructure.Email;
+
+namespace API.Specs.Mocks;
+
+/// <summary>
+/// Mock email service for testing that doesn't actually send emails.
+/// Tracks sent emails for verification in tests if needed.
+/// </summary>
+public class MockEmailProvider : IEmailProvider
+{
+   public List<SentEmail> SentEmails { get; } = new();
+
+   public Task SendAsync(string to, string subject, string body, bool isHtml = true)
+   {
+      SentEmails.Add(new SentEmail
+      {
+         To = [to],
+         Subject = subject,
+         Body = body,
+         IsHtml = isHtml,
+         SentAt = DateTime.UtcNow
+      });
+
+      return Task.CompletedTask;
+   }
+
+   public Task SendAsync(IEnumerable<string> to, string subject, string body, bool isHtml = true)
+   {
+      SentEmails.Add(new SentEmail
+      {
+         To = to.ToList(),
+         Subject = subject,
+         Body = body,
+         IsHtml = isHtml,
+         SentAt = DateTime.UtcNow
+      });
+
+      return Task.CompletedTask;
+   }
+
+   public void Clear()
+   {
+      SentEmails.Clear();
+   }
+
+   public class SentEmail
+   {
+      public List<string> To { get; init; } = new();
+      public string Subject { get; init; } = string.Empty;
+      public string Body { get; init; } = string.Empty;
+      public bool IsHtml { get; init; }
+      public DateTime SentAt { get; init; }
+   }
+}

src/Core/API/API.Specs/TestApiFactory.cs

@@ -1,7 +1,10 @@
 using System.Collections.Generic;
+using API.Specs.Mocks;
+using Infrastructure.Email;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Mvc.Testing;
 using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
 
 namespace API.Specs
 {
@@ -10,6 +13,20 @@ namespace API.Specs
         protected override void ConfigureWebHost(IWebHostBuilder builder)
         {
             builder.UseEnvironment("Testing");
+
+            builder.ConfigureServices(services =>
+            {
+                // Replace the real email service with mock for testing
+                var descriptor = services.SingleOrDefault(
+                    d => d.ServiceType == typeof(IEmailProvider));
+
+                if (descriptor != null)
+                {
+                    services.Remove(descriptor);
+                }
+
+                services.AddScoped<IEmailProvider, MockEmailProvider>();
+            });
         }
     }
 }

src/Core/Core.slnx

@@ -12,6 +12,8 @@
         <Project Path="Domain.Exceptions/Domain.Exceptions.csproj"/>
     </Folder>
     <Folder Name="/Infrastructure/">
+        <Project Path="Infrastructure/Infrastructure.Email/Infrastructure.Email.csproj"/>
+        <Project Path="Infrastructure/Infrastructure.Email.Templates/Infrastructure.Email.Templates.csproj"/>
         <Project Path="Infrastructure/Infrastructure.Jwt/Infrastructure.Jwt.csproj"/>
         <Project Path="Infrastructure/Infrastructure.PasswordHashing/Infrastructure.PasswordHashing.csproj"/>
         <Project Path="Infrastructure/Infrastructure.Repository/Infrastructure.Repository.csproj"/>

src/Core/Infrastructure/Infrastructure.Email.Templates/Components/Footer.razor

@@ -0,0 +1,18 @@
+<tr>
+   <td style="padding: 30px 40px 40px 40px; text-align: center; border-top: 1px solid #eeeeee;">
+      @if (!string.IsNullOrEmpty(FooterText))
+      {
+         <p style="margin: 0 0 10px 0; font-size: 13px; line-height: 20px; color: #999999;">
+            @FooterText
+         </p>
+      }
+      <p style="margin: 0; font-size: 13px; line-height: 20px; color: #999999;">
+         This is an automated message. Please do not reply as this inbox is unmonitored.
+      </p>
+   </td>
+</tr>
+
+@code {
+   [Parameter]
+   public string? FooterText { get; set; }
+}

src/Core/Infrastructure/Infrastructure.Email.Templates/Components/Header.razor

@@ -0,0 +1,36 @@
+<tr>
+   <td style="padding: 0; background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%); border-radius: 8px 8px 0 0;">
+      <!--[if mso]>
+      <table border="0" cellpadding="0" cellspacing="0" width="100%" style="background-color: #f59e0b;">
+      <tr>
+      <td style="padding: 30px 40px;">
+      <![endif]-->
+      <table border="0" cellpadding="0" cellspacing="0" width="100%">
+         <tr>
+            <td style="padding: 30px 40px; text-align: center;">
+               <div style="font-size: 48px; margin-bottom: 12px; line-height: 1;">🍺</div>
+               <h1
+                  style="margin: 0; font-size: 32px; color: #ffffff; font-weight: 700; letter-spacing: -0.5px; text-shadow: 0 2px 4px rgba(0,0,0,0.1);">
+                  The Biergarten App
+               </h1>
+               <div
+                  style="margin-top: 8px; font-size: 14px; color: rgba(255,255,255,0.9); font-weight: 500; letter-spacing: 2px; text-transform: uppercase;">
+                  Discover Your Perfect Brew
+               </div>
+            </td>
+         </tr>
+      </table>
+      <!--[if mso]>
+      </td>
+      </tr>
+      </table>
+      <![endif]-->
+   </td>
+</tr>
+
+<!-- Divider line -->
+<tr>
+   <td
+      style="padding: 0; height: 4px; background: linear-gradient(to right, #f59e0b, #d97706, #b45309, #d97706, #f59e0b);">
+   </td>
+</tr>

src/Core/Infrastructure/Infrastructure.Email.Templates/Infrastructure.Email.Templates.csproj

@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk.Razor">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <SupportedPlatform Include="browser" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference
+      Include="Microsoft.AspNetCore.Components.Web"
+      Version="10.0.1"
+    />
+    <PackageReference
+      Include="Microsoft.Extensions.DependencyInjection.Abstractions"
+      Version="10.0.1"
+    />
+    <PackageReference
+      Include="Microsoft.Extensions.Logging.Abstractions"
+      Version="10.0.1"
+    />
+  </ItemGroup>
+</Project>

src/Core/Infrastructure/Infrastructure.Email.Templates/Mail/UserRegistration.razor

@@ -0,0 +1,118 @@
+@using Infrastructure.Email.Templates.Components
+
+<!DOCTYPE html>
+<html lang="en" xmlns="http://www.w3.org/1999/xhtml" xmlns:v="urn:schemas-microsoft-com:vml"
+      xmlns:o="urn:schemas-microsoft-com:office:office">
+
+<head>
+   <meta charset="utf-8">
+   <meta name="viewport" content="width=device-width">
+   <meta http-equiv="X-UA-Compatible" content="IE=edge">
+   <meta name="x-apple-disable-message-reformatting">
+   <title>Welcome to The Biergarten App!</title>
+   <!--[if mso]>
+    <style>
+        * { font-family: Arial, sans-serif !important; }
+        table { border-collapse: collapse; }
+    </style>
+    <![endif]-->
+   <!--[if !mso]><!-->
+   <style>
+         * {
+            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
+         }
+   </style>
+   <!--<![endif]-->
+</head>
+
+<body style="margin: 0; padding: 0; background-color: #f4f4f4; width: 100%;">
+   <!-- Wrapper table for email clients -->
+   <table role="presentation" border="0" cellpadding="0" cellspacing="0" width="100%"
+          style="background-color: #f4f4f4;">
+      <tr>
+         <td align="center" style="padding: 40px 10px;">
+            <!-- Main container -->
+            <!--[if mso]>
+                <table border="0" cellpadding="0" cellspacing="0" width="600" style="width: 600px;">
+                <tr>
+                <td>
+                <![endif]-->
+            <table role="presentation" border="0" cellpadding="0" cellspacing="0" width="100%"
+                   style="max-width: 600px; background-color: #ffffff; border-radius: 8px; box-shadow: 0 2px 8px rgba(0,0,0,0.1);">
+
+               <!-- Include branded header component -->
+               <Header />
+
+               <!-- Welcome message -->
+               <tr>
+                  <td style="padding: 40px 40px 20px 40px; text-align: center;">
+                     <h1 style="margin: 0; font-size: 28px; color: #333333; font-weight: 600;">
+                        Welcome Aboard!
+                     </h1>
+                  </td>
+               </tr>
+
+               <!-- Body content -->
+               <tr>
+                  <td style="padding: 10px 40px 30px 40px; text-align: center;">
+                     <p style="margin: 0; font-size: 16px; line-height: 24px; color: #666666;">
+                        Hi <strong style="color: #333333;">@Username</strong>, we're excited to have you join our
+                        community of beer enthusiasts!
+                     </p>
+                  </td>
+               </tr>
+
+               <!-- Confirmation button -->
+               <tr>
+                  <td style="padding: 10px 40px;">
+                     <table role="presentation" border="0" cellpadding="0" cellspacing="0" width="100%">
+                        <tr>
+                           <td align="center">
+                              <!--[if mso]>
+                                        <v:roundrect xmlns:v="urn:schemas-microsoft-com:vml" xmlns:w="urn:schemas-microsoft-com:office:word" href="@ConfirmationLink" style="height:50px;v-text-anchor:middle;width:250px;" arcsize="10%" stroke="f" fillcolor="#f59e0b">
+                                        <w:anchorlock/>
+                                        <center style="color:#ffffff;font-family:Arial,sans-serif;font-size:16px;font-weight:600;">Confirm Your Email</center>
+                                        </v:roundrect>
+                                        <![endif]-->
+                              <!--[if !mso]><!-->
+                              <a href="@ConfirmationLink" target="_blank" rel="noopener noreferrer"
+                                 style="display: inline-block; padding: 16px 48px; background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%); color: #ffffff; text-decoration: none; border-radius: 6px; font-size: 16px; font-weight: 600; min-width: 170px; text-align: center; box-shadow: 0 4px 6px rgba(245, 158, 11, 0.3);">
+                                 Confirm Your Email
+                              </a>
+                              <!--<![endif]-->
+                           </td>
+                        </tr>
+                     </table>
+                  </td>
+               </tr>
+
+               <!-- Link expiry notice -->
+               <tr>
+                  <td style="padding: 20px 40px 10px 40px; text-align: center;">
+                     <p style="margin: 0; font-size: 13px; line-height: 20px; color: #999999;">
+                        This confirmation link expires in 24 hours.
+                     </p>
+                  </td>
+               </tr>
+
+               <!-- Footer info -->
+               <EmailFooter FooterText="Cheers, The Biergarten App Team" />
+            </table>
+            <!--[if mso]>
+                </td>
+                </tr>
+                </table>
+                <![endif]-->
+         </td>
+      </tr>
+   </table>
+</body>
+</html>
+
+@code {
+   [Parameter]
+   public string Username { get; set; } = string.Empty;
+
+   [Parameter]
+   public string ConfirmationLink { get; set; } = string.Empty;
+}

src/Core/Infrastructure/Infrastructure.Email.Templates/Rendering/EmailTemplateProvider.cs

@@ -0,0 +1,58 @@
+using Infrastructure.Email.Templates.Mail;
+using Microsoft.AspNetCore.Components;
+using Microsoft.AspNetCore.Components.Web;
+using Microsoft.Extensions.Logging;
+
+namespace Infrastructure.Email.Templates.Rendering;
+
+/// <summary>
+/// Service for rendering Razor email templates to HTML using HtmlRenderer.
+/// </summary>
+public class EmailTemplateProvider(
+    IServiceProvider serviceProvider,
+    ILoggerFactory loggerFactory
+) : IEmailTemplateProvider
+{
+    /// <summary>
+    /// Renders the UserRegisteredEmail template with the specified parameters.
+    /// </summary>
+    public async Task<string> RenderUserRegisteredEmailAsync(
+        string username,
+        string confirmationLink
+    )
+    {
+        var parameters = new Dictionary<string, object?>
+        {
+            { nameof(UserRegistration.Username), username },
+            { nameof(UserRegistration.ConfirmationLink), confirmationLink },
+        };
+
+        return await RenderComponentAsync<UserRegistration>(parameters);
+    }
+
+    /// <summary>
+    /// Generic method to render any Razor component to HTML.
+    /// </summary>
+    private async Task<string> RenderComponentAsync<TComponent>(
+        Dictionary<string, object?> parameters
+    )
+        where TComponent : IComponent
+    {
+        await using var htmlRenderer = new HtmlRenderer(
+            serviceProvider,
+            loggerFactory
+        );
+
+        var html = await htmlRenderer.Dispatcher.InvokeAsync(async () =>
+        {
+            var parameterView = ParameterView.FromDictionary(parameters);
+            var output = await htmlRenderer.RenderComponentAsync<TComponent>(
+                parameterView
+            );
+
+            return output.ToHtmlString();
+        });
+
+        return html;
+    }
+}

src/Core/Infrastructure/Infrastructure.Email.Templates/Rendering/IEmailTemplateProvider.cs

@@ -0,0 +1,18 @@
+namespace Infrastructure.Email.Templates.Rendering;
+
+/// <summary>
+/// Service for rendering Razor email templates to HTML.
+/// </summary>
+public interface IEmailTemplateProvider
+{
+    /// <summary>
+    /// Renders the UserRegisteredEmail template with the specified parameters.
+    /// </summary>
+    /// <param name="username">The username to include in the email</param>
+    /// <param name="confirmationLink">The email confirmation link</param>
+    /// <returns>The rendered HTML string</returns>
+    Task<string> RenderUserRegisteredEmailAsync(
+        string username,
+        string confirmationLink
+    );
+}

src/Core/Infrastructure/Infrastructure.Email/IEmailProvider.cs

@@ -0,0 +1,30 @@
+namespace Infrastructure.Email;
+
+/// <summary>
+/// Service for sending emails via SMTP.
+/// </summary>
+public interface IEmailProvider
+{
+    /// <summary>
+    /// Sends an email to a single recipient.
+    /// </summary>
+    /// <param name="to">Recipient email address</param>
+    /// <param name="subject">Email subject line</param>
+    /// <param name="body">Email body (HTML or plain text)</param>
+    /// <param name="isHtml">Whether the body is HTML (default: true)</param>
+    Task SendAsync(string to, string subject, string body, bool isHtml = true);
+
+    /// <summary>
+    /// Sends an email to multiple recipients.
+    /// </summary>
+    /// <param name="to">List of recipient email addresses</param>
+    /// <param name="subject">Email subject line</param>
+    /// <param name="body">Email body (HTML or plain text)</param>
+    /// <param name="isHtml">Whether the body is HTML (default: true)</param>
+    Task SendAsync(
+        IEnumerable<string> to,
+        string subject,
+        string body,
+        bool isHtml = true
+    );
+}

src/Core/Infrastructure/Infrastructure.Email/Infrastructure.Email.csproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <RootNamespace>Infrastructure.Email</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="MailKit" Version="4.9.0" />
+  </ItemGroup>
+</Project>

src/Core/Infrastructure/Infrastructure.Email/SmtpEmailProvider.cs

@@ -0,0 +1,126 @@
+using MailKit.Net.Smtp;
+using MailKit.Security;
+using MimeKit;
+
+namespace Infrastructure.Email;
+
+/// <summary>
+/// SMTP email service implementation using MailKit.
+/// Configured via environment variables.
+/// </summary>
+public class SmtpEmailProvider : IEmailProvider
+{
+    private readonly string _host;
+    private readonly int _port;
+    private readonly string? _username;
+    private readonly string? _password;
+    private readonly bool _useSsl;
+    private readonly string _fromEmail;
+    private readonly string _fromName;
+
+    public SmtpEmailProvider()
+    {
+        _host =
+            Environment.GetEnvironmentVariable("SMTP_HOST")
+            ?? throw new InvalidOperationException(
+                "SMTP_HOST environment variable is not set"
+            );
+
+        var portString =
+            Environment.GetEnvironmentVariable("SMTP_PORT") ?? "587";
+        if (!int.TryParse(portString, out _port))
+        {
+            throw new InvalidOperationException(
+                $"SMTP_PORT '{portString}' is not a valid integer"
+            );
+        }
+
+        _username = Environment.GetEnvironmentVariable("SMTP_USERNAME");
+        _password = Environment.GetEnvironmentVariable("SMTP_PASSWORD");
+
+        var useSslString =
+            Environment.GetEnvironmentVariable("SMTP_USE_SSL") ?? "true";
+        _useSsl = bool.Parse(useSslString);
+
+        _fromEmail =
+            Environment.GetEnvironmentVariable("SMTP_FROM_EMAIL")
+            ?? throw new InvalidOperationException(
+                "SMTP_FROM_EMAIL environment variable is not set"
+            );
+
+        _fromName =
+            Environment.GetEnvironmentVariable("SMTP_FROM_NAME")
+            ?? "The Biergarten";
+    }
+
+    public async Task SendAsync(
+        string to,
+        string subject,
+        string body,
+        bool isHtml = true
+    )
+    {
+        await SendAsync([to], subject, body, isHtml);
+    }
+
+    public async Task SendAsync(
+        IEnumerable<string> to,
+        string subject,
+        string body,
+        bool isHtml = true
+    )
+    {
+        var message = new MimeMessage();
+        message.From.Add(new MailboxAddress(_fromName, _fromEmail));
+
+        foreach (var recipient in to)
+        {
+            message.To.Add(MailboxAddress.Parse(recipient));
+        }
+
+        message.Subject = subject;
+
+        var bodyBuilder = new BodyBuilder();
+        if (isHtml)
+        {
+            bodyBuilder.HtmlBody = body;
+        }
+        else
+        {
+            bodyBuilder.TextBody = body;
+        }
+
+        message.Body = bodyBuilder.ToMessageBody();
+
+        using var client = new SmtpClient();
+
+        try
+        {
+            // Determine the SecureSocketOptions based on SSL setting
+            var secureSocketOptions = _useSsl
+                ? SecureSocketOptions.StartTls
+                : SecureSocketOptions.None;
+
+            await client.ConnectAsync(_host, _port, secureSocketOptions);
+
+            // Authenticate if credentials are provided
+            if (
+                !string.IsNullOrEmpty(_username)
+                && !string.IsNullOrEmpty(_password)
+            )
+            {
+                await client.AuthenticateAsync(_username, _password);
+            }
+
+            await client.SendAsync(message);
+            await client.DisconnectAsync(true);
+        }
+        catch (Exception ex)
+        {
+            throw new InvalidOperationException(
+                $"Failed to send email: {ex.Message}",
+                ex
+            );
+        }
+    }
+}

src/Core/Service/Service.Auth/Auth/RegisterService.cs

@@ -1,6 +1,9 @@
 using System.Threading.Tasks;
 using Domain.Entities;
 using Domain.Exceptions;
+using Infrastructure.Email;
+using Infrastructure.Email.Templates;
+using Infrastructure.Email.Templates.Rendering;
 using Infrastructure.PasswordHashing;
 using Infrastructure.Repository.Auth;
 
@@ -8,7 +11,9 @@ namespace Service.Auth.Auth;
 
 public class RegisterService(
     IAuthRepository authRepo,
-    IPasswordInfrastructure passwordInfrastructure
+    IPasswordInfrastructure passwordInfrastructure,
+    IEmailProvider emailProvider,
+    IEmailTemplateProvider emailTemplateProvider
 ) : IRegisterService
 {
     public async Task<UserAccount> RegisterAsync(UserAccount userAccount, string password)
@@ -23,19 +28,36 @@ public class RegisterService(
         }
 
 
-
         // password hashing
         var hashed = passwordInfrastructure.Hash(password);
 
-        // Register user with hashed password
+        // Register user with hashed password and get the created user with generated ID
-        return await authRepo.RegisterUserAsync(
+        var createdUser = await authRepo.RegisterUserAsync(
             userAccount.Username,
             userAccount.FirstName,
             userAccount.LastName,
             userAccount.Email,
             userAccount.DateOfBirth,
             hashed);
-    }
 
 
+        // Generate confirmation link (TODO: implement proper token-based confirmation)
+        var confirmationLink = $"https://thebiergarten.app/confirm?email={Uri.EscapeDataString(createdUser.Email)}";
+
+        // Render email template
+        var emailHtml = await emailTemplateProvider.RenderUserRegisteredEmailAsync(
+            createdUser.FirstName,
+            confirmationLink
+        );
+
+        // Send welcome email with rendered template
+        await emailProvider.SendAsync(
+            createdUser.Email,
+            "Welcome to The Biergarten App!",
+            emailHtml,
+            isHtml: true
+        );
+
+        return createdUser;
+    }
 }

src/Core/Service/Service.Auth/Service.Auth.csproj

@@ -12,6 +12,10 @@
   <ItemGroup>
     <ProjectReference Include="..\..\Domain.Entities\Domain.Entities.csproj" />
     <ProjectReference Include="..\..\Domain.Exceptions\Domain.Exceptions.csproj" />
+    <ProjectReference
+      Include="..\..\Infrastructure\Infrastructure.Email\Infrastructure.Email.csproj" />
+    <ProjectReference
+      Include="..\..\Infrastructure\Infrastructure.Email.Templates\Infrastructure.Email.Templates.csproj" />
     <ProjectReference
       Include="..\..\Infrastructure\Infrastructure.Repository\Infrastructure.Repository.csproj" />
     <ProjectReference